protect against default qt keybinding that crashes the tree view

qtgui/instrument.py

@@ -113,7 +113,8 @@ class InstrumentTreeController(object):
 
 
     def itemExpandedOrCollapsed(self, libraryItem:QtWidgets.QTreeWidgetItem):
-        api.session.guiSharedDataToSave["libraryIsExpanded"][libraryItem.id] = libraryItem.isExpanded()
+        if type(libraryItem) is GuiLibrary : #just in case
+            api.session.guiSharedDataToSave["libraryIsExpanded"][libraryItem.id] = libraryItem.isExpanded()
 
     def itemSelectionChanged(self):
         """Only one instrument can be selected at the same time.